Samsung Viewfinity S9 and M1 iMac - Weird screen artifacts

When I connect the Samsung Viewfinity S9 5k display to my iMac, the image on the Samsung display does not look kosher. I note the iMac has Thunderbolt 3 and the Samsung has Thunderbolt 4, but can that really be the issue? The iMac is capable of driving 5k 50hz via Thunderbolt 3 as far as I understand? These are my iMac's specs: https://www.apple.com/by/imac-24/specs/
These are the Samsung Viewfinity S9 specs: https://www.samsung.com/za/monitors/high-resolution/viewfinity-s9-27-inch-5k-resolution-ls27c902pauxen/ I seems my iMac (old one first gen M series) is Thunderbolt 3. The samsung is Thunderbold 4